In order to manufacture a light emitting diode for a light source of a backlight, a method has been used in which a light emitting chip is mounted on a printed circuit board or a lead frame and then a molding portion for enveloping the light emitting chip is formed by a transfer molding process. FIGS. 1 to 3 are views illustrating such a conventional manufacturing method of a chip-type light emitting diode, wherein FIGS. 1(a) and 2(a) are plan views, FIGS. 1(b) and 2(b) are sectional views, and FIG. 3 is a perspective view showing the conventional chip-type light emitting diode.
Referring to FIG. 1, light emitting chips 12 are mounted on a substrate 11 such as a printed circuit board or a lead frame. The substrate 11 has lead electrodes (not shown), and the light emitting chips are electrically connected to the lead electrodes via wires 13.
Referring to FIG. 2, the substrate 11 on which the light emitting chips 12 are mounted is positioned within a mold die (not shown), and molding portions 14 are then formed by the transfer molding process. Conventionally, the mold die has runners through which a molding material can flow, and the light emitting chips are positioned within the runners. Accordingly, the molding portions 14 are formed along the rows of the light emitting chips as shown in the figure. Then, the substrate 11 is separated through a sawing process to obtain individual light emitting diodes as shown in FIG. 3.
According to the prior art, there are advantages in that the chip-type light emitting diodes can be mass-produced by forming the molding portions using the transfer molding process, and materials with large specific gravity such as inorganic phosphors can be uniformly dispersed in the molding portions 14 due to shorter molding time.
However, since the molding portions 14 for enveloping the light emitting chips 12 are transparent, light emitted from the light emitting chips 12 is emitted outwards through entire surfaces of the molding portions 14. Accordingly, there are disadvantages in that a range of directional angles of light is broader to cause reduction in light emission intensity within a desired range of directional angles, and light which is not used for backlighting increases, which results in a higher loss of light. Further, since cut surfaces at both sides of the substrate are coextensive with those of the molding portions as shown in FIG. 3, there is a disadvantage in that second molding portions cannot be formed on the cut surfaces of the molding portions 14.
Meanwhile, in order to improve the light emission intensity within a desired range of directional angles, a manufacturing method of a reflector-type light emitting diode has been used in which reflectors are attached to a substrate or formed by injection-molding an opaque synthetic resin, light emitting chips are mounted thereon, and then transparent molding portions are formed inside the reflectors.
The manufacturing method of such a reflector-type light emitting diode has an advantage in that light emission intensity within a desired range of directional angles can be improved. However, since it is difficult to form the transparent molding portions through a transfer molding process, a process of potting a liquid phase resin inside the reflectors has been generally used. Since the liquid phase resin should be separately potted inside the respective reflectors in the process of potting the liquid phase resin, productivity is lowered. Further, since it takes a great deal of time to perform the molding process so that phosphors with large specific gravity go down, it is difficult to provide molding portions with the phosphors dispersed uniformly therein. Moreover, the technique of attaching the reflectors or forming the reflectors using injection molding has a limitation on reduction in the thickness of each of light emitting diodes.
An object of the present invention is to provide a manufacturing method of a light emitting diode in which a first molding portion formed by a transfer molding process is positioned within a region encompassed by cut surfaces of a substrate.
Another object of the present invention is to provide a manufacturing method of a light emitting diode, which has a symmetrical, second molding portion formed on side surfaces of the first molding portion.
A further object of the present invention is to provide a manufacturing method of a light emitting diode capable of improving light emission intensity within a desired range of directional angles.
A still further object of the present invention is to provide a manufacturing method of a light emitting diode that has a reflector, the method being able to prevent the thickness of the light emitting diode from being increased.
To solve the technical problems, a manufacturing method of a light emitting diode according to an aspect of the present invention comprises the step of preparing a substrate. Light emitting chips are mounted on the substrate, and an intermediate plate is positioned on the substrate. The intermediate plate has through-holes for receiving the light emitting chips and grooves for connecting the through-holes to one another on an upper surface of the intermediate plate. Then, a transfer molding process is performed with a transparent molding material by using the grooves as runners so as to form first molding portions filling the through-holes. Thereafter, the intermediate plate is removed, and the substrate is separated into individual light emitting diodes. Accordingly, since the first molding portions are formed in the through-holes of the intermediate plate, it is possible to provide a light emitting diode in which the first molding portion is positioned within a region encompassed by cut surfaces of the substrate.
Meanwhile, the transparent molding material may contain phosphor powders. Accordingly, since the first molding portions are formed by performing the transfer molding process with the transparent molding material containing the phosphor powders, the phosphors can be prevented from going down in the first molding portions.
The intermediate plate may be positioned on the substrate before the light emitting chips are mounted. Thereafter, the light emitting chips may be mounted in the through-holes of the intermediate plate.
Meanwhile, in an embodiment of the present invention, after the intermediate plate is removed, second molding portions for surrounding at least side surfaces of the first molding portions may be formed.
In some embodiments of the present invention, the second molding portions may be formed by performing molding out of an opaque molding material to cover the first molding portions and by removing the opaque molding material until upper surfaces of the first molding portions are exposed. Alternatively, the second molding portions may be formed by performing molding out of an opaque molding material to fill spaces between the first molding portions while exposing the upper surfaces of the first molding portions. The second molding portions formed out of the opaque molding material may serve as reflectors to improve light emission intensity within a desired range of directional angles. Since the second molding portions are formed to be flush with the first molding portions, it is possible to prevent an increase in the thickness of the light emitting diode.
In some embodiments of the present invention, the second molding portions may be molded out of a transparent molding material to have lens portions for covering the respective upper surfaces of the first molding portions. The lens portion is used to focus light emitted from the light emitting chip within a range of directional angles, thereby improving light emission intensity.
Meanwhile, the second molding portions for surrounding at least side surfaces of the first molding portions may be formed to be spaced apart from one another. Further, the second molding portions may cover upper surfaces of the first molding portions and contain phosphors. Accordingly, it is possible to provide a light emitting diode in which the second molding portion containing the phosphors is uniformly formed on the first molding portion. The second molding portions may be formed by using another intermediate plate that has through-holes for receiving the first molding portions.
A manufacturing method of a light emitting diode according to another aspect of the present invention comprises the step of preparing a substrate. Light emitting chips are mounted on the substrate, and first transparent molding portions for covering the respective light emitting chips are formed. Then, second opaque molding portions for covering side surfaces of the first molding portions are formed, and the substrate is separated into individual light emitting diodes. Accordingly, it is possible to manufacture a light emitting diode in which an increase in the thickness thereof can be prevented and light emission intensity within a desired range of directional angles can be improved.
The second molding portions may be formed by performing molding out of an opaque molding material to cover the first molding portions, and by removing the opaque molding material until the upper surfaces of the first molding portions are exposed. Alternatively, the second molding portions may be formed by performing molding out of an opaque molding material to fill spaces between the first molding portions while exposing the upper surfaces of the first molding portions.
According to the present invention, it is possible to manufacture a light emitting diode in which a first molding portion formed through a transfer molding process is positioned within a range encompassed by cut surfaces of a substrate so that a second molding portion can be symmetrically formed on side surfaces of the first molding portion. Accordingly, the second molding portion may be formed to serve as a reflector or to have a lens portion, thereby improving light emission intensity within a desired range of directional angles. If the second molding portion with the function of the reflector is selected, it is possible to prevent an increase in the thickness of the light emitting diode contrary to a conventional chip-type light emitting diode, and to remarkably improve light emission intensity within a desired range of directional angles.